Antarctic Star HZB-12B Portable Automatic Ice Maker Repair
The HZB-12/B is also sold as the AGLUCKY Z5880-RED. The HZB-12B is a very clever design.
This is my first look at ice makers, so perhaps it is a common design. The manufacturer tells me there is no service manual available. Here's some of what I discovered as I
worked on repairing a unit.
The user manual is located here. Note the schematic on page 8, an exploded view with parts list on
page 9, and a customer service phone number on the back cover.
Referring to the schematic, here are a few comments.
The "water level detecting" is actually more of a flow detector. Water is pumped up to the ice making box. Just before it is sent into the ice making box, it passes through
a grounded metal elbow. There is a thin metal wire hanging down into the water stream just as it exits the elbow. The microcontroller detects conductivity between this wire
and the grounded metal elbow to detect that water is flowing. If the microcontroller runs the pump and does not see this conductivity, the system is shut down and the Add Water
LED is lit.
The infrared sensor has an LED on one side of the area where the ice scoop pushes the ice into the ice basket and the sensor on the other. When the ice basket is full,
the IR beam is interrupted. The system shuts down and the Ice Full LED lights. If the machine is in an area with a lot of sunlight, the IR sensor detects the sunlight and
does not detect ice full. The system will keep making ice even when full. This could result in the ice making box getting jammed and parts breaking.
The two microswitches detect the end of travel of the synchronous motor that rotates the ice making box. The switches just tell the microcontroller to stop rotation. The
gear assembly in the motor switch rotation direction when the motor hits a stop.
The condensor temperature sensor appears to be a thermistor hanging by its leads within the cabinet.
The Motor For Ice Shovel is the self reversing synchronous motor discussed later.
The Solenoid Valve is probably the valve that puts hot refrigerant in the ice probes at the end of the cycle to drop the ice from the probes.
I did get a response via SMS text message when I left a message with the customer support number. They wanted a video showing the symptoms (below). They then incorrectly determined
that the problem was the LED board and sent me a new one (shipped direct from China). However, the board they sent was for a different system and did not fit in this one. In addition, the LED board was fine. As
discussed below, the issue was the synchrnonous motor that tips the ice making box and the ice shovel. As further discussed below, I got the motor from Ali Express, but it does
appear that the manufacturer can supply parts.
The system is driven by a microcontroller (the chip with the label on top in the second photo at the right). High current DC peripherals such as the water pump are driven by a
ULN2003A Darlington array.
Though the block diagram in the manual indicastes there is a water level detecting switch,
the "water level" detection is actually a flow detection. A collar through which water shoots into the freeze trough is grounded. Another wire hangs down into the stream
of water. If the stream of water is present, current is detected between the wire and the collar. If the microcontroller turns on the pump and no water flow is detected,
the system stops and the "add water" LED is lit.
The "ice shovel" motor is a self reversing synchronous motor.
The microcontroller controls the ice shovel motor using an opto coupled triac driving a small
triac to switch 120 VAC to the motor. The motor switches direction when the rotation of the shaft is blocked. This motor rotates the freeze trough which has a panel
on the front of it. As the trough is rotated to horizontal, the panel (the "ice shovel") pushes ice out to the ice basket. The opposite end of the shaft from the motor has a lever that
hits stops to reverse the motor direction and also hits microswitches to tell the microcontroller that the shaft has reached the end of its rotation. At one end of its rotation, the
freeze trough is vertical (to dump out excess water and allow the ice to drop), and at the other it is horizontal to hold water that is to be frozen.
This motor is an exact replacement for the ice shovel motor. It comes
with leads that are the correct length and connectors ready to plug onto the PCB. The lead colors are red and white, while the original ones were black and white, but this
makes no difference.
Block diagram of system from User Manual
Front view of PCB
Back view of PCB
Reversing synchronous motor
Lever on end of freeze trough shaft hits stop and microswitch at each end of rotation
This video shows the system in operation. The video starts with the end of one ice production cycle. Note that ice has formed around
the cooling probes that are poked into the water. The microcontroller runs the refrigeration system for one period of time for small ice cylinders, and a longer time
for larger ones. When the freeze cycle is done, the trough is rotated to vertical, dumping the excess water. The freezing probes are then heated (possibly by sending
hot compressed refrigerant to the probes) causing the ice to break free of the freezing probes. The synchronous motor then rotates the freezing trough back to horizontal
as the ice shovel (panel with slots in it) pushes the ice into the ice storage basket. The freezing trough is then refilled with water. Note the wire hanging down into the
stream of water. The microcontroller detects conductivity between this wire and a collar that the water is flowing through. If the pump runs for a period of time and
conductivity through the water is not detected, the system stops and the "Add Water" LED lights. Note that the freezing trough is overfilled and water drains back into
the water reservoir at the bottom of the unit. The overfilling ensures that the trough is filled even if the pump is not perfect. No water level detector is needed, and
precision timing of the water flow is not required. Once the water pump stops, the freezing cycle repeats.
Video of ice making cycle
Though not the problem with this particular unit, this video shows how to disassemble the unit and unclog a water pump.
This video shows the original symptoms on this unit. At first, it appeared that there was something wrong with the "water level" sensor
since the Add Water LED did not come on when no water was present. As discussed above, it was later discovered that it is a water flow sensor instead of a water level
sensor, so the Add Water LED would not light until the pump tried to pump water to the freeze trough and found no flow. Since the Select button properly toggles between
the L and S LEDs, the microcontroller is probably working.
About 15 minutes after power up, the Add Water and the Ice Full LEDs alternate. Though not clear at the time, this is apparently a signal from the microcontroller
that something in the sequence has not gone correctly. As mentioned in the video, there was no DC current through the pump motor. Looking at the PCB with a scope, I found
that the open collector output of the ULN2003A driving the pump had 12V on it. It should be near ground to run the pump. The corresponding input of the
ULN2003A was low, so the microcontroller is not telling the pump to run. At this point, I still did not know what the proper sequence of operations was for the
system. Repeatedly hitting one of the microswitches driven by the freeze trough shaft resulted in the water pump starting. At this point, a clamp on AC ammeter
was put around one of the wires going to the synchronus motor driving the freeze trough. There was current, but the motor was not rotating.
Video of problem symptoms
Since the motor was getting current but not rotating, it was removed for inspection. The result is shown in the image at the right. The shaft could not be rotated
in either direction. Some WD-40 was sprayed on the shaft and bushing bearing, and the shaft gently worked back and forth until free. Then a liberal amount of
Valvoline synthetic SAE 0W-20 oil, the same I use on my Teletypes, was applied to the junction of the shaft and the bushing.
The motor was then powered for several minutes to allow the oil to work into the bearing. Now and then, the shaft would be grabbed with pliers to simulate the shaft
hitting a stop. After several tries, the motor properly reversed direction. The motor was then reinstalled and the video at the top of this page, showing proper operation,
was shot. At this point, the unit has worked properly for about 24 hours producing at least 20 baskets of ice. However, the motor eventually froze again.
A replacement was ordered. The new one was an exact replacement
except for the color of the leads. The leads were the right length and included the connectors to plug onto the PCB.
Synchronous motor removed showing corrosion.
Second Failure
After several weeks operation, I found that the ice box that holds the water during the freeze would not rotate to horizontal. Instead,
it would move slightly from vertical, then stop and attempt to fill it with water. The problem was the top limit switch was jammed.
The button on the microswitch was depressed and would not come back out. A replacement switch was found
here. Note that the switch has a straight lever arm. The ones received had a
curl at the end like these. The "curl" ran into a plastic strut. I cut off the
curl and all is well. It's working again!
I look forward to comments and information on other problems people have found. In general, if the ice shovel does not move when power first applied, and the water pump does not run,
have a look at the synchronous motor.
